1. Field of the Invention
The present invention relates to a control valve of a refrigeration cycle employed in a variable capacity compressor, and in particular relates to a control valve for a variable capacity compressor that controls supply of coolant gas into a crank chamber from a delivery pressure region as required and to discharge of coolant gas into a suction-side region in the crank chamber.
2. Description of the Related Art
Since the compressor that is employed in the refrigeration cycle of an air conditioner for an automobile is directly coupled with the engine by means of a belt, it is not possible to control the speed of rotation thereof. A variable capacity compressor is therefore employed whose compression capacity (delivery rate) can be altered in order to obtain an appropriate cooling capability without being influenced by the rotational speed of the engine.
This variable capacity compressor typically has a construction in which coolant that is drawn in from a suction chamber communicating with a suction conduit is compressed and delivered into a delivery chamber communicating with a delivery conduit and in which the delivery rate of coolant is changed by change of coolant pressure of a pressure-regulated chamber (crank chamber) that is subjected to coolant pressure control by means of a control valve. Japanese Patent Application Laid-open No. 2002-303262 discloses a control valve for a refrigeration cycle that controls the coolant pressure Pc of a crank chamber by producing a flow (gas suction) of delivered coolant from a delivery conduit passage (delivered coolant pressure Pd) into the crank chamber (crank chamber coolant pressure Pc) by opening/closing a valve arranged on the gas suction side, in accordance with the coolant pressure balance of the suction coolant pressure Ps of a variable capacity compressor and the reaction of a bellows. Regulation of the crank chamber coolant pressure Pc of the variable capacity compressor can be achieved by this means.
However, in regulatory control of the crank chamber coolant pressure Pc of the aforesaid variable capacity compressor, there are limitations on the response thereof in that for example a prescribed time is required from when a fluctuation of the suction coolant pressure Ps takes place until completion of control. Realization of a control valve having a function wherein response is further improved is therefore desired.